Remote storage may be implemented for computer systems wherein one or more computing device is provided access to one or more storage devices via a network. Remote storage offers many advantages, including providing access to one or more storage devices from multiple locations, upgrading/replacing storage devices without interrupting other data processing operations, and providing for failover strategies. Failover strategies in a storage network enable a computing device to continue accessing a storage device in the storage network via an alternate path if one path becomes disabled.
There are a wide variety of different types of failover strategies for storage networks. Some failover strategies are implemented manually, e.g., by a user reconfiguring a path to the storage device if the user is unable to access the storage device via the currently configured path. Such manual approaches can be time-consuming and require the user to understand at least the basic infrastructure of the storage network and how to reconfigure access via an alternate path. In addition, manual approaches are not suitable for adaptive infrastructures which are expected to be fully automated.
Automated failover strategies include direct host-to-target communication. In host-to-target communication, the computing device desiring access to the storage device may issue a high-layer communication to the storage device. If the computing device receives a reply from the storage device, the path is known to be working. If, however, the computing device does not receive a reply from the storage device, the path is assumed to have failed and the computing device automatically fails over to an alternate path.
Unfortunately, linking devices in the network may be inoperative at a higher communications level (e.g., at the software or firmware level) without interrupting the path at a lower physical level (e.g., at the circuit level). But because the computing device does not receive a reply from the storage device, the computing device unnecessarily fails over to the alternate path. In addition, high-level host-to-target communications can interrupt legitimate system drivers and software applications on the computing device.